Washington County, which manages campgrounds at both the Lake Elmo Park Reserve and St Croix Bluffs Regional Park, does a great job of maintaining campgrounds, trails, and bathroom facilities at both parks. St Croix Bluffs is right along the St. Croix river - in the summer you can hang out at the sandy beach on the river and in the fall there are many trails to enjoy fall color.
There are multiple areas in the modern campground - one section is for larger rigs that has 50 amp service and water at each site, most sites in the other loops have 20 or 30 amp electric service, and there are a few non-electric tent-only sites as well. The park prohibits both pets and alcohol! There is both a volleyball court and nice play structure in the modern campground.
We camped over MEA break (mid October) at site #4 this year and liked how close it was to the bathroom building. There is a lot of open space behind the parking/tent pad on this site, which made it a perfect spot for the kids to run and play without running close to other camper's sites. Sites 1, 2, 4, and 6 have similar amounts of open space behind the campsites.
In the past we've stayed here as part of a group in the group campsite. The group campsites at this park are some of the best I've stayed in - they include sand volleyball courts, a covered picnic shelter with electricity, a primitive toilet, and access to a large play structure nearby.